POLIO
Polio is a crippling disease that infects the gastrointestinal tract and spreads to the central nervous system. Polio can cause permanent paralysis in children. Like smallpox, polio relies on human-to-human transmission, so it can be eradicated if the last remaining chains of infection are broken.

1955
Development of the Polio VaccineFollowing the growth of virus in culture by John F. Enders, Frederick Robbins, and Thomas H. Weller in 1949, Jonas Salk formulated an inactivated virus vaccine, which was given by injection.

1962
Oral Polio Vaccine
Albert Sabin introduced a live attenuated vaccine that could be given orally, which became the standard for vaccination.

Jonas Salk (left) and Albert Sabin (right) developed vaccines against polio. Salk formulated the first inactivated virus vaccine, which was given by injection. Seven years later, Sabin introduced a live attenuated virus that had the advantage that it could be given orally. (Photos from the National Library of Medicine)